WO 03/075832A2 indicates that attenuated biotransformation of GTN by the enzyme mitochondrial aldehyde dehydrogenase (mtALDH, ALDH2) underlies nitrate tolerance, i.e., the loss of clinical sensitivity to GTN. WO 03/075832A2 discloses a number of therapies for reversing, postponing or preventing the occurrence of nitrate tolerance.